English-native speaker: Correct for me, please!

[english-learner]

Does this sentence sound English/American style?

"Learning is similar to rowing a boat upstream. If you cannot travel forward(s), you must be go backward(s)"
Or
"Learning/Studying is compared to rowing a boat upstream. It must be go downstream if not travel upstream'

Which sounds better? and your own sentence?

Thank a lot in advance

[fadedjeans]

Thank you very much for your help. I'm a math-teacher so it's very helpful.

btw: You write "different speed" but in American I've read they write "distinct speed"
In addition, in some math-web, I recognize " uniform speed", "constant speed" I think uniform speed and constant speed are the same meanings. Is it right?


Anyway, I think:

It took a canoe 4 hours to travel downstream from A to B and 5 hours to go upstream from B to A

This is written correctly. "uniform" and "constant" Gramtically they have the same meaning. When talking about "speed" -- constant speed is used most.

[english-learner]

I need to translate into English a mathematical sentence that makes me confused, who can help?

1.Let H be the foot of the altitude from A to BC
2.Let H be the foot of the right-angled line drawn from A to BC
3.Let H be the right-angled projection of A to BC


What sentence is right?
If they are all right, what sentence is the most popular used?

[dethuong_x0x]

I need to translate into English a mathematical sentence that makes me confused, who can help?

1.Let H be the feet of the altitude from A to BC
2.Let H be the feet of the right-angled line drawn from A to BC
3.Let H be the right-angled projection of A to BC


What sentence is right?
If they are all right, what sentence is the most popular used?

Number 2 and 3 are little confused for me... I like number 1 better but I would like to fix it a little bit:

Let H be the intercept point of the altitude from A to BC.

[justdoit]

I need to translate into English a mathematical sentence that makes me confused, who can help?

1.Let H be the feet of the altitude from A to BC
2.Let H be the feet of the right-angled line drawn from A to BC
3.Let H be the right-angled projection of A to BC


What sentence is right?
If they are all right, what sentence is the most popular used?

In math terms, A is usually meant a point & BC is a segment.
Base on your sentences, here is what I get.
1.Let H be the feet of the altitude from A to BC
My interpretation:
A
|
|
|
|
H |
_____|___________
B C

2.Let H be the feet of the right-angled line drawn from A to BC
My interpretation:
A
|
|
|
|
|__________
B H C

3.Let H be the right-angled projection of A to BC [I’m not sure what you meant in this sentence, especially the projection part]
My interpretation:
A
|\
| \
| \
| \ H
| \
|______\
B C
FYI – for the above right triangle, the sides are called as:
AB is the height
BC is the base
And AC is the Hypotenuse

So now back to your questions

What sentence is right?
All 3 are correctly stated, i'm not sure what you are looking for

If they are all right, what sentence is the most popular used?
I don’t know how to answer that, since all 3 sentences are different!